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4.2.2.4
Examples on how to connect, configure and set CT inputs for most
commonly used CT connections
SEMOD55055-296 v5
Figure
defines the marking of current transformer terminals commonly used around the
world:
In the SMAI function block, you have to set if the SMAI block is measuring
current or voltage. This is done with the parameter:
AnalogInputType: Current/
voltage. The
ConnectionType: phase -phase/phase-earth and GlobalBaseSel.
I
Sec
I
P
ri
S1 (X1)
P1
(H1)
P2
(H2)
S2 (X2)
P2
(H2)
P1
(H1)
x
x
a)
b)
c)
en06000641.vsd
S2 (X2)
S1 (X1)
IEC06000641 V1 EN-US
Figure 12: Commonly used markings of CT terminals
Where:
a)
is symbol and terminal marking used in this document. Terminals marked with a square
indicates the primary and secondary winding terminals with the same (that is, positive)
polarity
b) and
c)
are equivalent symbols and terminal marking used by IEC (ANSI) standard for CTs. Note
that for these two cases the CT polarity marking is correct!
It shall be noted that depending on national standard and utility practices, the rated secondary
current of a CT has typically one of the following values:
•
1A
•
5A
However in some cases the following rated secondary currents are used as well:
•
2A
•
10A
The IED fully supports all of these rated secondary values.
It is recommended to:
•
use 1A rated CT input into the IED in order to connect CTs with 1A and 2A
secondary rating
•
use 5A rated CT input into the IED in order to connect CTs with 5A and 10A
secondary rating
Section 4
1MRK 505 343-UEN B
Analog inputs
66
Application manual
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